Good Sam Club Open Roads Forum: Tech Issues: Intermittent brake failure
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 > Intermittent brake failure

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Geraldo de La Cruz

zihuatanejo

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Posted: 12/24/21 11:38am Link  |  Quote  |  Print  |  Notify Moderator

I have been experiencing unusual brake failure in 2 vehicles, 2001 Ford F150, 2004 Dodge 1500. Both trucks have perfectly good brakes and operate as expected. Except in the following cases:

1 With a one day change in elevation from sea level to 8000 feet, the hydraulic system for the brakes in both trucks has intermittently failed completely, with the emergency brake being the primary way to stop the vehicle. This condition lasts for a few hours and then disappears as rapidly as it appeared.

2 The brakes function normally except during the occasional panic stop. 99% of the time the brakes function as expected however 1 % of the time even with full two foot pressure on the brakes, from about 5 to 10 mph - no lock up, no ABS vibration, simply a slow gentle stop - right into the vehicle in front of me.

Fluid level - check, Brake pads and calipers - check, rotors - check. No visible leaks.

Remember, the brakes are in working order, and they work properly 99% of the time.

I am at a loss to understand why this is happening. Any suggestions are welcome

Gdetrailer

PA

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Posted: 12/24/21 12:18pm Link  |  Quote  |  Print  |  Notify Moderator

Back to basics.

Pull the calipers and brake pads, inspect the slide surfaces of the pad ears.

The pad ears must glide across the slide surfaces with only light friction, often times the pad ears are slightly oversized and are hard to move by hand. Add in a little rust and the pads stick and freeze in the caliper. Depending on where they stick you can get no brakes or brakes work on and off or badly stuck they will not release from the rotor. I find I have to grind down the pad ears some to get them to slide easily by hand.

Inspect the caliper pins, this is a known part that often sticks, caliper pins should easily move in and out by hand, can get replacement pins at your local auto parts store.

Inspect the caliper hoses for kinks or damage, sadly these hoses often get damaged when mechanics fail to support the caliper and let it dangle in mid air when servicing the brakes. This causes the hose to kink internally which is not noticeable from the outside. Sometimes the hose deteriorates on the inside and collapses enough to block flow. For vehicles the age you are talking about, replacing the hoses may be in order just because of age.

Baring hose or physical pad/caliper you could have calipers that are way past due replacement time, some caliper cylinders use a plastic piston which over time deteriorates and gets stuck intermittently.

If all of those checks out fine, then perhaps your master cylinder may need replaced..

time2roll

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Posted: 12/24/21 12:22pm Link  |  Quote  |  Print  |  Notify Moderator

I would start with a complete fluid flush with a pressure bleeder. Second would be to replace the master cylinder.
Maybe just do both at the same time.

By failure I assume the peddle went to the floor without the expected braking action.


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gbopp

The Keystone State

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Posted: 12/24/21 02:42pm Link  |  Quote  |  Print  |  Notify Moderator

Is the Brake Pedal going to the floor or, you have enough Pedal but the brakes just don't stop the vehicle?

winnietrey

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Posted: 12/24/21 02:43pm Link  |  Quote  |  Print  |  Notify Moderator

Don't know about the Dodge, But that vintage Ford is famous for calipers sticking

KD4UPL

Swoope, VA

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Posted: 12/24/21 03:04pm Link  |  Quote  |  Print  |  Notify Moderator

Have you ever changed the brake fluid? If not it's high time.

wolfe10

Texas

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Posted: 12/24/21 04:29pm Link  |  Quote  |  Print  |  Notify Moderator

KD4UPL wrote:

Have you ever changed the brake fluid? If not it's high time.


AMEN!

How old is the brake fluid, and was the "failure" after using the brakes either hard or for a long time (like on a steep descent)?


Brett Wolfe
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Skibane

San Antonio, TX

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Posted: 12/24/21 05:28pm Link  |  Quote  |  Print  |  Notify Moderator

KD4UPL wrote:

Have you ever changed the brake fluid? If not it's high time.


That's very likely the culprit.

Brake fluid absorbs moisture from the air.

The more moisture it absorbs, the lower its boiling point becomes.

When it boils, it is no longer an incompressible liquid - so your brake pedal is no longer capable of applying any pressure on it.

Also, the boiling point of fluids decreases with altitude. The higher you go, the easier it becomes for the fluid to boil.

Finally, if the brake fluid has ever been previously replaced, it's possible that the replacement fluid has a lower boiling point than the manufacturer's engineers intended that vehicle to have (e.g., used DOT3 replacement fluid in a vehicle designed to use DOT4 fluid):

[image]

(The "dry" boiling points shown on the chart are for brand-new brake fluid, and the "wet" boiling points are for fluid that has had a chance to absorb some moisture.)

* This post was last edited 12/24/21 07:42pm by Skibane *   View edit history

Geraldo de La Cruz

zihuatanejo

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Posted: 12/25/21 08:26am Link  |  Quote  |  Print  |  Notify Moderator

Thank you for all your thoughts. The brake problem is so random. It only happens once every few years. Nothing obvious like brake fade. I think I will start by changing the brake fluid and then work my way towards the master cylinder.

jdc1

Rescue, Ca

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Posted: 12/25/21 11:05am Link  |  Quote  |  Print  |  Notify Moderator

I would check the vacuum pressure system too. 20 year old hoses tend to get minute cracks.

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